Allowance For Loan Loss - Past Due and Non-Accrual Loans (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Schedule of Aging of Financing Receivables [Line Items]
Number of days a loan must be paid current before accrual of interest is resumed	180 days
Loans 30-59 Days Past Due	$ 4,692,000	$ 2,189,000
Loans 60-89 Days Past Due	226,000	1,184,000
Non-accrual loans	21,570,000	21,601,000
Total Past Due Loans	26,488,000	24,974,000
Current Loans	1,422,355,000	1,336,074,000
Gross loans	1,448,843,000	1,361,048,000
Number of days past due, majority of loans 30-59 days past due	30 days
The ratio of non-accrual loans to total loans	1.49%	1.59%	1.93%
Additional funding commitments for loans on non-accrual	592,000
Commercial real estate | Commercial real estate
Schedule of Aging of Financing Receivables [Line Items]
Loans 30-59 Days Past Due	1,921,000	1,560,000
Loans 60-89 Days Past Due	183,000	551,000
Non-accrual loans	12,645,000	12,608,000
Total Past Due Loans	14,749,000	14,719,000
Current Loans	771,245,000	695,546,000
Gross loans	785,994,000	710,265,000
Commercial real estate | Commercial construction
Schedule of Aging of Financing Receivables [Line Items]
Loans 30-59 Days Past Due	727,000	0
Loans 60-89 Days Past Due	0	0
Non-accrual loans	1,442,000	743,000
Total Past Due Loans	2,169,000	743,000
Current Loans	114,179,000	120,624,000
Gross loans	116,348,000	121,367,000
Commercial and industrial | Commercial and industrial
Schedule of Aging of Financing Receivables [Line Items]
Loans 30-59 Days Past Due	449,000	472,000
Loans 60-89 Days Past Due	34,000	55,000
Non-accrual loans	5,997,000	6,993,000
Total Past Due Loans	6,480,000	7,520,000
Current Loans	337,029,000	321,059,000
Gross loans	343,509,000	328,579,000
Residential | Residential
Schedule of Aging of Financing Receivables [Line Items]
Loans 30-59 Days Past Due	1,500,000	42,000
Loans 60-89 Days Past Due	0	558,000
Non-accrual loans	995,000	862,000
Total Past Due Loans	2,495,000	1,462,000
Current Loans	120,209,000	118,816,000
Gross loans	122,704,000	120,278,000
Residential | Home Equity
Schedule of Aging of Financing Receivables [Line Items]
Loans 30-59 Days Past Due	85,000	73,000
Loans 60-89 Days Past Due	0	9,000
Non-accrual loans	477,000	390,000
Total Past Due Loans	562,000	472,000
Current Loans	74,077,000	75,176,000
Gross loans	74,639,000	75,648,000
Consumer | Consumer
Schedule of Aging of Financing Receivables [Line Items]
Deposit liabilities reclassified as loans receivable, 90 days or more past due	8,000	5,000
Loans 30-59 Days Past Due	10,000	42,000
Loans 60-89 Days Past Due	9,000	11,000
Non-accrual loans	14,000	5,000
Total Past Due Loans	33,000	58,000
Current Loans	5,616,000	4,853,000
Gross loans	5,649,000	4,911,000
Not Adversely Classified
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	1,421,277,000	1,326,613,000
Non-accrual loans not adversely classified	1,100,000	1,200,000
Not Adversely Classified | Commercial real estate | Commercial real estate
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	770,741,000	688,266,000
Not Adversely Classified | Commercial real estate | Commercial construction
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	112,663,000	118,381,000
Not Adversely Classified | Commercial and industrial | Commercial and industrial
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	336,997,000	321,078,000
Not Adversely Classified | Residential | Residential
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	121,324,000	119,024,000
Not Adversely Classified | Residential | Home Equity
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	73,943,000	74,987,000
Not Adversely Classified | Consumer | Consumer
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	$ 5,609,000	$ 4,877,000